Molding composition



Patented Sept. 3, 1940 v I PATE T oFFIc MOl DING COMPOSITION David E. Cordier, Toledo, Ohio, assignor to Plaskon Company, Incorporated, Toledo, Ohio, a corporation of Delaware I No Drawing;

Application September 13, 19:38, Serial N0. 229,785

The invention rel es to plastlcizd formaldehyde-urea molding compositions.

i Formaldehyde-urea. molding compositions are thermosetting, i. e., when-molded under elevated pressure and temperature they first. soften and then harden at the molding temperature. A thermoplastic molding composition, in: contrast,

remains soft until the molded'article has cooled. Although an article molded from a thermosetting composition can be removed from the mold after 7 a relatively short time and while the article is still hot, an article molded from a thermoplastic composition'cannotbe removed from the mold until it has cooled, and thus-hardened sufiijciently so that it does not become blistered ordistorted upon release of the pressure. -Thelength of time.

for which a molding. composition must be-left in the mold is one of the .factors that determines the cost of articles molded from the composition. A composition that must be left in the mold twice as long as another composition requires about twice as much moldingequipment for the same volume of production, and hot-moldingequipment is'expensive. i

-Although the thermosetting character of formaldehyde-urea molding compositions is highly'advantageous,'thesoftening of such compositions that occurs in the mold before set-- ting or hardening takes place is very important.

3 A'thermosetting composition that does not unas a streaked surface in the case of a colored article. The surface appearance that is produced by failure-of a molding composition to soften before setting is known as dog skin. When a ,molding composition does not soften sufficiently in the mold, bubbles or'pockets of gas are frequently trapped, and produce flaws in the finished article her. completely softened granules cemented together,

Although acid substances have been used as plasticizers in formaldehyde-urea molding compositions containing no cellulose, such substances cannot be usedin a composition containing cel-I lulose as a filler, because they render it unstable and cause rapid-deterioration. Formaldehydeurea molding compositions containing no cellulose have not been found satisfactory for commercial use. g

To be suitable for use as a plasticizer, a sub- Y stance should not be so alkaline as to prevent the formaldehyde-urea molding composition from hardening in-the mold.; Substances that are highly soluble in water cannotbe used as plasticizers because they seriously impair-the resistant properties of a formaldehyde-urea resin.

v Phenol-has been suggested as a plasticizer for formaldehyde-urea moldingcompositions, but it is unsatisfactory because it imparts an undesirable' color and odor to thecompositions'. Moreover, the color of a formaldehyde-urea composition containing phenol is so unstable that the composition would. have to be handled in a refrigerated dark room to prevent the appearance,

of the molded articles-from being spoiled. Toluene sulfonamides have been used for want of better plasticizers, but-their plasticizing efiect is 7 so slight that they are of little value.

Only substances that are soluble in formaldehyde-urea resin can be used as plasticizers, because insoluble substances bleed out of theresin and thus spoi-l molded articles in which they are;

used. The substances that are soluble in formaldehyde-urea resin are very limited in nummolecularstructure similar to'that of the resin;

Most of such substances seem to have a' for example,fcertain urea derivativesare soluble in formaldehyde-urea resin. However, urea derivatives in general do not have a plasticizing efieot upon formaldehyde-urea molding composi-.

tions. Urea itself cannot be used as a plasticizer dehyde-urearesin and capable of appreciably plasticizing a formaldehyde-urea molding composition are extremely rare.

The principal object of the invention is to probecause of its deleterious effect upon the product. The substances that are both soluble' in formalvide formaldehyde-urea molding compositions containing novel plasticizers. More specific objects and advantages are apparent from-the de- 'scription, which merely discloses and illustrates the invention and is not intended-to impose limitations upon the claims.

A molding composition embodying the invention contains a plasticizer selected from the group consisting of organic compounds of the general formula o o X-NlI-lL-NH-Y-Nik--NH-Cfla-OH in which X is H or and Y is ethylene, propylene or 2-hydroxytri- "methylene. Plasticizers illustrative of the general formula stated above are (1) compounds ofthe general formula o o X-NH-LNH-CHr-CH:NH NHCH:-OH in which X is H (monomethylol ethylene diurea) in which X is H (monomethylol propylene diurea) or 0H CH4 (dimethylol propylene diurea); and -(3) compounds of the general formula in which X is H (monomethylol 2-hydroxytri-- methylene diurea) or (dimethylol Y 2-hydroxytrimethylene. diurea). Each of these substances may be prepared by reacting the corresponding diurea with formaldehyde.

Propylene diurea may be prepared as follows:

Urea. (120 parts) is refluxed with 100 parts of a per cent aqueous solution of propylene diamine until the evogution of ammonia ceases. 144 parts of a crude p oduct, or 88 parts of pure propylene diurea melting at 192-193 C. can be obtained.

A plasticizer embodying the invention can be prepared from the corresponding diurea as follows: The diurea is dissolved in a 40 per cent aqueous solution of formaldehyde having a pH of 'l to 7.4. The resulting solution is kept at about C. for about; three-quarters of an hour as The water is then evaporated at temperatures less than about 60 C. until the dry crystals are obtained. If the dimethylol derivative is desired,

the molar ratio of formaldehyde to the diurea should be 2:1. If the monomethylol derivative is desired, the molar ratio should be 1:1. A formaldehyde-urea molding composition of the usual type, consisting primarily of cellulosic ma-.-

. terial (40 to 50%) and a formaldehyde-urea reaction product, may be employed.

Example A dried formaldehyde-urea molding composition containing 35 parts of alpha-cellulose fiber impregnated with 50 parts of 9. formaldehydeurea reaction product is ground in a'ball mill, together with 4 parts of monomethylol propylene diurea. The customary modifiers, such as lubricants, accelerators, and coloringmatter, may also be added to the ball mill. After an intimate mixture has been obtained in the form of a fine powder, it may be granulated or formed into pellets so that it can be used conveniently for charging molds. 'The molding able pressure at a temperature of about 0.

Various applications of the invention may be devised to meet various requirements.

Having described my invention, I claim: 1

1. A thermosetting molding composition comprising a formaldehyde-urea reaction product and a plasticizer selected from the group consisting of organic compounds of the general formula of Hand /0H is performed under a suit- -'2. A formaldehyde-urea molding composition comprising a formaldehyde-urea reaction product, cellulosic material, and a plasticizer selected from the groupconsisting of organic compounds of the general formula in which X is a member of the group consisting of H and Y I comprising dimethylol ethylene diurea as' a plasticizer.

5. A formaldehyde-urea molding composition comprising monomethylol propylene diurea as a. plasticizer.

DAVID E. CORDIER. 

